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Essay
Chronic Obstructive Pulmonary Disease: A Growing but Neglected Global Epidemic Peter J. Barnes
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hronic obstructive pulmonary disease (COPD) is a major and increasing global health epidemic that has received insufficient attention from the health-care profession, governments, and the pharmaceutical industry. Urgent action is now required to recognise the disease, predicted to soon become one of the major causes of death and disability, and to develop more effective prevention and treatment strategies.
What Is COPD? COPD is described by the Global Initiative for Chronic Obstructive Lung Disease as “a preventable and treatable disease…characterized by airflow limitation that is not fully reversible. The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lung to noxious particles or gases” [1]. This progressive and relentless loss of lung function is caused by emphysema due to destruction of lung parenchyma and by narrowing of small airways as a result of chronic inflammation and fibrosis and loss of elastic recoil. This results in progressive airflow limitation, air trapping, and progressive shortness of breath on exertion.
The Size of the Problem The Global Burden of Disease studies ranked COPD as the sixth commonest cause of death worldwide in 1990, and it was predicted to become the third commonest cause by 2020 [2]. A more recent projection from the World Health Organization predicts that it will rise from its current ranking as fifth commonest cause of death to be the fourth commonest by 2030, behind only ischemic heart disease, cerebrovascular disease, and HIV/AIDS [3]. The increase is predicted to be greater in developing countries than affluent countries. Indeed, COPD is The Essay section contains opinion pieces on topics of broad interest to a general medical audience.
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the only common cause of death in the United States that has increased over the last 40 years, in sharp contrast to the reduction in cardiovascular and infectious diseases. Even more importantly, COPD is an increasing cause of chronic disability and is predicted to become the fifth most common cause of chronic disability worldwide by 2020 [2]. The prevalence of COPD is approximately 10% in the general population throughout the world [4,5]. Many patients with COPD remain undiagnosed even when the disease causes severe disability [6]. Consultation rates for COPD in general practice in the United Kingdom now exceed those of ischemic heart disease by 2-4-fold, and COPD is one of the commonest causes of hospital admission in the UK [7]. COPD is also one of the commonest reasons for time lost from work, placing an enormous and increasing economic burden on society. This has resulted in major health-care expenditure that now exceeds the costs of asthma by over 3-fold [6]. The reasons for the global increase in COPD include continuing cigarette smoking amongst men, with increasing smoking amongst women, and the longer survival of populations; these changes are particularly relevant in developing countries.
The Neglect of COPD Despite growing recognition as an important international health problem, COPD has suffered neglect from clinicians, researchers, and the pharmaceutical industry [8]. This is largely because COPD is viewed as self-inflicted (by smoking) and also because the underlying disease process is generally perceived to be irreversible. Consequently, there is a fundamental lack of knowledge about the cellular, molecular, and genetic causes of COPD. Existing therapies for COPD are inadequate and none have been shown to slow the relentless progression of the disease. In terms of research funding, COPD has been
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relatively neglected among common diseases, with little investment in research into its underlying cellular and molecular mechanisms. COPD is now recognised to have the greatest socioeconomic inequality of any common disease and is commonly a disease of the poor, suggesting that there are environmental factors other than smoking contributing to the disease. Indeed, over 10% of patients with a clinical diagnosis of COPD are non-smokers, and this proportion is much higher amongst women in developing countries such as India, where exposure to biomass fuels in an enclosed space is an important cause of COPD [9].
Natural History The classical epidemiological studies of Fletcher and Peto demonstrated that death and disability from COPD were related to an accelerated decline in lung function with time, with a loss of 50–100 ml in forced expiratory volume in one second (FEV1) per year, compared to the normal loss of
